Abstract Recently, fuel cells especially direct methanol fuel cells (DMFCs), have attracted great interest because of their high energy density, their pollution‐free operation mode and thus their prospect for use in convenient transportation. Although platinum (Pt) catalyst is an efficient catalysts for DMFCs, it has some problems such as high price, poor stability and durability. Therefore, the research of high performance Pt catalysts becomes the focus. Firstly, the hyperbranched polyglycerols (HPG) were synthesized by the one‐step anionic ring‐opening polymerization. The Pt‐Au bimetallic catalysts supported on reduced graphene oxide (Pt‐Au‐HPG/rGO) were synthesized via a hydrothermal method, using HPG as the template and stabilizer. The electrocatalytic performances for the electrooxidation of methanol were investigated by electrochemical methods. Compared with commercial Pt/C (10 wt %) catalysts, Pt‐Au‐HPG/rGO has the larger electrochemically active surface area (ECSA, 108.8 m 2 g −1 ), higher catalytic performance (0.498 A mg metal −1 ) and better stability. This excellent performance is attributed to the good dispersion and conductivity of Pt‐Au‐HPG/rGO for the addition of HPG, rGO and Au. Meanwhile, the bifunctional and electronic effects between Au and Pt improved the electrochemical performance of the samples.
The booming electric vehicle industry continues to place higher requirements on power batteries related to economic-cost, power density and safety. The positive electrode materials play an important role in the energy storage performance of the battery. The nickel-rich NCM (LiNixCoyMnzO2 with x + y + z = 1) materials have received increasing attention due to their high energy density, which can satisfy the demand of commercial-grade power batteries. Prominently, single-crystal nickel-rich electrodes with s unique micron-scale single-crystal structure possess excellent electrochemical and mechanical performance, even when tested at high rates, high cut-off voltages and high temperatures. In this review, we outline in brief the characteristics, problems faced and countermeasures of nickel-rich NCM materials. Then the distinguishing features and main synthesis methods of single-crystal nickel-rich NCM materials are summarized. Some existing issues and modification methods are also discussed in detail, especially the optimization strategies under harsh conditions. Finally, an outlook on the future development of single-crystal nickel-rich materials is provided. This work is expected to provide some reference for research on single-crystal nickel-rich ternary materials with high energy density, high safety levels, long-life, and their contribution to sustainable development.
In order to accurately simulate the actual road driving resistance of four-wheel drive motor vehicles based on the chassis dynamometer and efficiently test the vehicle performance, it is necessary to analyze the influencing factors of the additional loss resistance and the loading resistance of the chassis dynamometer bench system. In this paper, the effects of the drum speed, the sampling speed interval, and basic inertia on the test results of the additional loss resistance are tested and analyzed based on the self-developed chassis dynamometer of a four-wheel drive motor vehicle. The static and dynamic components of the additional loss resistance are defined by linear regression through ordinary least squares, and the additional loss resistance of the four-axis eight-drum chassis dynamometer and mainstream chassis dynamometer system for four-wheel drive motor vehicles are compared. In addition, the effects of the dynamometer type and the control strategy on the loading resistance are discussed, and the transient condition, steady-state condition, and overall operating condition deviation coefficient of loading force are defined, according to which the advantages and disadvantages of the control strategy of the chassis dynamometer system for four-wheel drive motor vehicles are evaluated. The analysis of the influencing factors and laws of the resistance of the four-wheel drive motor vehicle chassis dynamometer bench system can provide a reference basis for accurately simulating the resistance of vehicle road driving based on the bench testing.
The emerging altermagnetic RuO2 with both compensated magnetic moments and broken time-reversal symmetry possesses nontrivial magneto-electronic responses and nonrelativistic spin currents, which are closely related to magnetic easy axis. To probe the N\'eel order in RuO2, we conducted Ru M3-edge X-ray magnetic linear dichroism (XMLD) measurement. For epitaxial RuO2 films, characteristic XMLD signals can be observed in either RuO2(100) and RuO2(110) at normal incidence or RuO2(001) at oblique incidence, and the signals disappear when test temperature exceeds N\'eel temperature. For nonepitaxial RuO2 films, the flat lines in the XMLD patterns of RuO2(100) and RuO2(110) demonstrate that there is no in-plane uniaxial alignment of N\'eel order in these samples, due to the counterbalanced N\'eel order of the twin crystals evidenced by X-ray diffraction phi-scan measurements. Our experimental results unambiguously demonstrate the antiferromagnetism in RuO2 films and reveal the spatial relation of N\'eel order to be parallel with RuO2 [001] crystalline axis. These research findings would deepen our understanding of RuO2 and other attractive altermagnetic materials applied in the field of spintronics.
Lithium–sulfur (Li–S) batteries have attracted great attention owing to their excellent electrochemical properties, such as the high discharge voltage of 2.3 V, specific capacity of 1675 mA h g−1 and energy density of 2600 Wh kg−1. The widely used slurry made electrodes of Li–S batteries are plagued by the serious shuttle effect and insulating nature of sulfur. Herein, a reduced graphene oxide coated porous carbon nanofiber flexible paper (rGO@S-PCNP) was fabricated and directly used as an additive-free cathode for Li–S batteries. The results show that the rGO@S-PCNP is certified to be effective at relieving the shuttle effect and improving the conductivity, thus achieving high electrochemical performance. The rGO@S-PCNP composite with a sulfur content of 58.4 wt% delivers a high discharge capacity of 623.7 mA h g−1 after 200 cycles at 0.1 C (1 C = 1675 mA g−1) with the average Coulombic efficiency of 97.1%. The excellent cyclability and high Coulombic efficiency indicate that the as-prepared rGO@S-PCNP composite paper can be a promising cathode for lithium–sulfur batteries, and is envisioned to have great potential in high energy density flexible power devices. This facile strategy brings great significance for large-scale industrial fabrication of flexible lithium–sulfur batteries.
Abstract Lithium-ion (Li-ion) batteries have been widely used in portable electronic devices and new energy vehicles in recent years. Although commercial graphite anode has good safety and low cost, its low theoretical capacity cannot better meet the demand for higher-capacity of power batteries. As an excellent electrode material, copper sulfide (Cu 2 S) has the advantages of high capacity and stability. Herein, Cu 2 S deposited on carbon paper (Cu 2 S@CP) was prepared by simple copper electrodeposition on carbon paper and sulphidation, which can be used to the anode of Li-ion batteries directly. Based on the three-dimensional structure of carbon paper and the high capacity of copper sulfide, the composite anode shows good lithium storage performance, which provides a new possibility for commercial power lithium-ion battery anode materials.
Mo-doped SnO2 nanoparticles were prepared via a facile hydrothermal method in this work, demonstrating excellent long-cycling performance as anode material for LIBs.
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